WI: Henry III, Duke of Brabant inherits Boulogne instead of Adelaide of Auvergne

Looks like a strict primogeniture or proximity was in operation here (ie regardless of gender).
If so then Adelaide only got it from her older sister Maria dying some months before. And her younger sister Mathilde who was older than Henry died in 1267.
Keep Maria alive past Adelaide's death 1261 and past Matilde's death in 1267. Then her successor will be a choice between Floris V of Holland (great nephew via Mathilde) or John I of Brabant ( great nephew via Henry II).
 
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